linux-kernel - Re: [PATCH 2/2] Markers Implementation for Preempt RCU Boost Tracing

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Date:	Fri, 4 Jan 2008 16:28:58 +0530
From:	Gautham R Shenoy <ego@...ibm.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	"K. Prasad" <prasad@...ux.vnet.ibm.com>, mingo@...e.hu,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	dipankar@...ibm.com, paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH 2/2] Markers Implementation for Preempt RCU Boost
	Tracing

On Thu, Jan 03, 2008 at 11:30:55AM -0500, Mathieu Desnoyers wrote:
> * K. Prasad (prasad@...ux.vnet.ibm.com) wrote:
> > This patch converts the tracing mechanism of Preempt RCU boosting into
> > markers. The handler functions for these markers are included inside
> > rcupreempt_trace.c and will be included only when PREEMPT_RCU_BOOST is
> > chosen.
> >  
> > Signed-off-by: K.Prasad <prasad@...ux.vnet.ibm.com>
> > ---
> >  include/linux/rcupreempt_trace.h |   46 ++++++++
> >  kernel/rcupreempt-boost.c        |  211 ++++-----------------------------------
> >  kernel/rcupreempt_trace.c        |  183 +++++++++++++++++++++++++++++++++
> >  3 files changed, 251 insertions(+), 189 deletions(-)
> >  
> > Index: linux-2.6.24-rc2-rt1.MARKER_PATCHES_NEW/include/linux/rcupreempt_trace.h
> > ===================================================================
> > --- linux-2.6.24-rc2-rt1.MARKER_PATCHES_NEW.orig/include/linux/rcupreempt_trace.h
> > +++ linux-2.6.24-rc2-rt1.MARKER_PATCHES_NEW/include/linux/rcupreempt_trace.h
> > @@ -102,5 +102,51 @@ extern int rcupreempt_flip_flag(int cpu)
> >  extern int rcupreempt_mb_flag(int cpu);
> >  extern char *rcupreempt_try_flip_state_name(void);
> >  
> > +#ifdef CONFIG_PREEMPT_RCU_BOOST
> > +struct preempt_rcu_boost_trace {
> > +	unsigned long rbs_stat_task_boost_called;
> > +	unsigned long rbs_stat_task_boosted;
> > +	unsigned long rbs_stat_boost_called;
> > +	unsigned long rbs_stat_try_boost;
> > +	unsigned long rbs_stat_boosted;
> > +	unsigned long rbs_stat_unboost_called;
> > +	unsigned long rbs_stat_unboosted;
> > +	unsigned long rbs_stat_try_boost_readers;
> > +	unsigned long rbs_stat_boost_readers;
> > +	unsigned long rbs_stat_try_unboost_readers;
> > +	unsigned long rbs_stat_unboost_readers;
> > +	unsigned long rbs_stat_over_taken;
> > +};
> > +
> > +#define DEFINE_PREEMPT_RCU_BOOST_MARKER_HANDLER(preempt_rcu_boost_var) \
> > +void preempt_rcu_boost_var##_callback(const struct marker *mdata, \
> > +				void *private_data, const char *format, ...) \
> > +{ \
> > +	va_list ap; \
> > +	int cpu; \
> > +	struct preempt_rcu_boost_trace *boost_trace; \
> > +	va_start(ap, format); \
> > +	cpu = va_arg(ap, typeof(unsigned int)); \
> 
> (sorry for late response, I just came back from vacation)
> 
> Instead of passing the cpu id as a marker parameter, why don't you
> simply use smp_processor_id() right here ?
> 

Agreed. 

Also in patch 1, in cases where we're using markers in place of RCU_TRACE_ME(), 
we need not pass the parameter and simply use smp_processor_id().

It's only the RCU_TRACE_RDP() that requires cpuid to be passed.


Thanks and Regards
gautham.


> -- 
> Mathieu Desnoyers
> Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

-- 
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
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